Electronic computing device



J. A. RAJCHMAN ETAL ELECTRONIC COMPUTING DEVICE Dec. 23, 1947.

2 Sheets-Sheet 1 Filed Nov. 29, 19.41

ZSmaentoiS FEED 806A Ill/.

T675 a c. M m w a u a 'J. A. RAJCHMAN ET AL I 5 ELECTRONIC COMPUTING "DEVICE Filed Nov. 29, 1941 2 sheets-sheet 2 IIII 11|||||||||- Q V II I I gs-L J Wow M-lllllll NET M -mmr 'v I ll llllll I 'r''''' nun l III!!! I I!" Smsentorg Patented Dec. 23, 1947 UNITED "STAT ES PATENT 2,433,236

ELECTRONIC ooMfiifitiniivi'ii Jan A. Rajchman, Philadelphia Pa and Richard Snyder, Jr., Glassboro; 5N;-

Radio Corporation of America, a Corporation of Delaware 'zi'fisiiest'iaa navaatei 29, rein serial fiwitmtc I anemia (01; Eat-ti) '1 2 I This invention e1 to elsotidiiitcb'ffiifiiitifi devicesand has-fur ts principalfobject to pro de a noveland reliab e method andmeans for th tamin substantiany in tantaneously a voltage which is propd'rtionalto the; product'of twogiven alternating current voltages.

Another and important object (if the present invention "is did provide an electronic computing device capable-6f simultaneously solving several difierent, or indeed similar, problems in multipli cation.

/ It has been disclosed by Rajchman and Morton in co-pending application-Serial No. 408,870, filed August 29, 1941,:now abandoned; and replaced by the continuation in part application Serial No.

528,882, filed Marchiil, 19114, that twolelec tronic squaring devicescafi 'be used to multiply, since the difierence between the squares of the sum and difference of two iiuinbers is proportional to their product; The-present invention discloses-a-method of multiplication which-re quires the use otbut one squaring device, irre' spective' of'the number of multipliers and multiplicands involved.

The two .given "A.=-G.- 'vol'ta gsyof Which the productis desired'fmaybe'constant or variable.- The present disclosure is notespeeially concerned- With the utilization ofthe' said product though "it may here b'e mentioned that the invention finds useful applicatidn not only in devices which may be considered ems-electronic equivalents of conventional mechanical-' computing machines but also in electro=mechanicaIcontrolsystems for directing anti-aircraft fire, and l the like and wherein computations Based on rapidly Varying.

data must, for optimum results, be completed with extremerafilditi l v The principle of the invention, together with dtliei'idldic'ts" afiwadv'antages and certain int fefred details ofdor'istrutitiori, w'n be explained'in the followingspeeificatien'wit reference to" the a ompanyiri diawifies;wherein: h M Figure 1 isa' partly sch -emeticariaagemem an apparatusjwlthinthe inven 101i, forobtai g, simultaneously; svel al'el'ctricafvalues 'ach pro a: and 1 Thdrsulti'ng yoltae 632,0 ivoltages may be i'ndiatecl-*tin-"suitably calibrated meters M1, M2, and M3, and may be otherwise utilized; if desired. The voltages to be multiplied are supplied, in the instant casefby oscillators X1, Y1, X2, Y2, and X3,

fee i ate-tee varied, manually or automatically, in agreement with the multipliers andinultiplicands supplied 1hacdidahcfiwithtfi invention; the tude controlled A Q. outputs of the oscill n u on aD-G.

the grid 1, and lens sy'sten if-il ll, l3 and are sub- Jc't to the influencedfa'chstant magnetic field which is applied in a direction perpendicular to the plane defined by electric field and the axis of the beam as by mansof acoil or yoke l5 surrounding-the tubeadiiacentthe deflecting el'ec-' trodes 'Dx land-Dy: -'Ih-e zyoke J5 is hereshown' energized by a battery I! having a-variableresistor 19 in series therewith- The application (in addition to the D.-C. voltage suppliediby 'batteries'= B116- and By) of the Ai -C. volt-ages, frombscil'latorsx and Y tothe deflecting: plates Db: and' By, respectively, of the tube T prduces aslight'deflection-of the electron beam inthe-tube and a res'ulting difference in electron fldw 'td the s'eparateparts I' and 3 of the bi-part target. *A* feedback circuit l later' de'scrib'ed in" connectiomwith'Fig 2'-)"*c' onnected"to the'separate" awaefthe erget iareduces anamp uof the electron flow to the separate parts of the target. This amplified signa1 voltage is impressed upon the cathode 5 and thus adjusts it to the potential (negative with respect to ground, and the accelerating electrodes 9 and 13) required to prevent deflection of the beam by the electric and magnetic fields present between the deflecting plates Da: and Dy. Electrical filters F1, F2, and F3 connected between the cathode 5 and accelerating electrode 9, 13 are each designed to pass (to the meters Ml, M2 and M3, respectively) a frequency component of one of the said signal voltages proportional to either the sum or to the difference of the frequencies (a: and y) originally applied to the deflecting plates Dar: and Dy.

Before proceeding with a detailed description of the feedback circuit shown in Fig. 2, it may be well to explain the principle and theory upon which the present invention is predicated.

It is well known that the deflection d of the electron beam in a cathode ray tube due to an electric field E is where V is the voltage through which the electrons have been accelerated before they enter the field E, and c is a constant which depends upon the geometry of the tube. Similarly, for a uniform magnetic field H the deflection is given by where a is a constant which depends upon the geometry of the tube. Should the electric and magnetic fields be other than uniform, then the same relations (1) and (2) still hold and E and H are values of the fields at a particular point, and the constants a and have appropriate values.

Suppose now that the electric and magnetic fields are in the same physical space and that they tend to deflect the beam in opposite directions. When there is no deflection the trajectory of the beam remains a straight line and it can be made to strike two collecting plates separated by a negligible distance. Thus the currents to the two plates are equal. As soon as there is a slight deflection the currents to the two plates become unequal, and their difference may be considered as a signal. This signal may be used to control the value of the accelerating voltage V in such a way as to keep the beam undefiected for any arbitrarily chosen values of E and H. We will have then E H =a- 3 0V /V or E ==A H V (4) If the magnetic field is maintained constant, the relation between E and V according to (4) becomes simply IcE v 5 This Equation 5 shows that a deflection tube with electrostatic and magnetic deflection may be employed as a squaring device. It has already been shown (in copending application Ser. No. 408,870, filed August 29, 1941, to Rajchman and Morton) that two squaring devices can be made to multiply, since the difference between the squares of the sum and difference of two numbers is proportional to their product. However, a. deflection tube similar to that shown in Figs. 1 and 2 lends lli 1 2) rt znl In other words, the voltage V will have constant terms, terms of frequency Zen and 2oz and terms of frequency (oi-m2) or (w1+w2) It will be noted that the terms of frequency (w1w2) or (wl+w2) have an amplitude which is proportional to the unknown product my. Therefore if an appropriate band pass filter is used in the circuit of V which passes only frequencies neighboring (w1w2) or (wi-I-wz), the output of this filter will be pr portional to the product of the given amplitudes a: and y.

As indicated in Fig. 1 the device of the invention is capable of performing several multiplications simultaneously. In this case let E be equal to:

E=a sin ti t-Fa sin w t+ a sin w t+ a sin co t (9) then, by substitution in Equation 5:

All the terms of the first sum given constant terms or terms whose frequencies are 2:01. Every term of the second double sum can be expressed in terms of two terms of frequencies wi-wx and wi-l-wk, respectively. The amplitude of the term (i, x) is m at. Therefore if a series of filters (F Fig. 1) tuned to the frequencies vi-wk (or w1+w are inserted in the circuit of V they will pass amplitudes proportional, respectively, to a: a) Thus, it is possible to multiply simultaneously any two of the n coefficients m to an one by another. It may be noted also that one of the frequencies used can be zero. In this case the resultant A.-C. amplitude will be proportional to a D.-C. voltage and to an A.-C. voltage, as shown by:

Attention is also called to the fact that the energy required to drive the electrostatic deflecting plates is very small as compared to that which would be necessary if the magnetic field were to vary at the same rapid rate of change. Thus the fact that the magnetic field remains constant renders the device of the invention practical.

From the foregoing it will be apparent that the operation of the device necessarily requires the use of circuit means which Will automatically so adjust the accelerating voltage V that the electron beam will be instantly restored to its normal straight or undefiected path for all combinations of the magnetic (H) and electric (E) fields, however rapid the variations of the latter field, One form of feedback circuit which will perform this adjustment is shown in detail in Fig, 2.

.sameiaszithezsimilarly desi nated tube. oiifii s l.

That is to say it employs the same arrangement i electrodes-and requiresrtheuseipf.butzasingleracicelerating .voltager sothat its.. iocus.- depends; Lessentialiy llnonaits; geometry. and remainsthe same substantiall wirresnective pf the particularvalue .orthesaid accelerating voltage; In practice however, it; wasrfound desirable .toadiust-thei poteniii-allot.thQmiddJeflBfiS element- I- lytwhichi is shown tin.

i .i3i?11 3101101118:zp fi l ifitl) .it a v otenti hti inegative with-'resn ettoithe cathode. .Th.e gridbias filfldi'tliI-G LGOIIU'O] *of the accelerating volt- .a ezare 'aefiecteddncthid embodiment of thei nvenitiongby meansofaufgeedbackcircuit from the 101- l tr at s 3 stotbe cathodeli- .flih e dback-ci cuit s wn.irrEi ;2 com rises atmush-nulliam iiyingtsta edc ns s n f. .twc apentode (WhefiKSltuhefi. heredesi nated Z-La tential. :The:signal iromsztheiother tube 23 of the 1 first push-pull stage drives the grid of another pentode 21 carrying a much smaller current (say 2 ma.) whose cathode is connected to the cathode of the heavy current tube 25. A large resistance 29 connects the cathodes of both tubes and 21 to ground. In this arrangement the potential of the cathode in the heavy current tube 25 follows the grid potential from one side (2 I) of the pushpull stage (2 I23) hence the potential of the cathode of the low current tube 21 also follows the said grid potential. The grid of the low cur rent tube 21, being driven by the other side (23) of the first push-pull circuit (2l-23) changes its potential in the opposite direction from its cathode. The plate of the low current tube 21 is connected through a resistor 3I to the plate supply 33. The output of this tube 21 is fed into a voltage divider which is connected to the plate of the low current tube 21 and to a source of potential 31, say 90 volts negative with respect to round. An arm 39 of the voltage divider 35 is connected to the grid of a high current (type 807) tube 41 which controls the potential of the cathode 5 of the deflection tube T, through a 1000-volt battery 43 and a voltage divider 45. The negative return of the battery 43 is connected to the voltage divider 45 whose other terminal is grounded at 41, closing the anode circuit of tube M, The appropriate potential for the middle electrode I I of the electron gun is obtained through arms 49 and 50, respectively, on the voltage divider 45. Since the electrodes 5, 1 and II are all connected to the same voltage divider 45 the ratios of their potentials will remain substantially constant irrespective of the voltage impressed upon the divider by tube 4 I.

The constant magnetic field impressed in the region of the deflecting plates Dr, Dy, is obtained by using an ordinary television deflecting yoke I5 connected, to a battery I1 as in Fig. 1. A D.-C.

..23,; reshectivel cworkin into. tw similar tubes-2 5 i5 :centerinstrnohcntialecnsathe 'defiecting-nplatesginc .anmnmisisuanliedinzom batteratlzithrou hsa ipbtenticmetem-fl. hel'lA'l lnotentials are;:de- :gfiblfidathd'fllEhLlI-L'flzdmfiktmh .yllasfinfligizlilzfmm itwo' omnoremsciliatorsitnot hQIB'iShOWH)JWh-0S8 amplitudeszareicontrnllediin P511011: away .that they aregpropcrtionalsmiths-numbers.toibezmultiplied. Mhererbuh woiinputryoltageszwere employed their .frequerieiesiwerechosenltorbeslQ00:cycles and .1600 cyclesaandxitheirtsfillfli:rcycle: .difierence :was; sufzficientlyshighitozsubstantialheeliminate-anystray 60 cycle nterierencezffromzzneaarbyrmains. .-.-The -.d1iferen fsrequencyvwasuohosenr in this.:case,:insteadopf... he rsum,-;:to::make surerzthatt..harmoni cs .ircnr eithenof the :inputfrequencies; wouldnotinteriere with. the output. ...'Iihe..filt.er.systemtusedto ..that=..component of-:.;-.theurcathodeirnQtential which waricsaat. a;.:ireguency .aneighboring 11.6.90 vclestandwhose amplitude representsthe; desired zproduct. my). .anonsistsn in. this -.case-,;.of a. number .otsimplerna aller resonant circuits 55, BI .'-.6;9..-:33.

145s: ashownrin 1g; 2 ,:..the first: parallel resonant fillrguit'l orifijlten 55.;is: coupled. to, .the cathode 510f th u e III-thr u h a..-.lar eresistor 5' :and-block- .in acapacitoreii ciliheasecond parallel resonant circuitifi [x -i5, coupledeto. .theiprecedin :cir uit.5.5 :byimeansz vof the pentode .63,-;a, blocking capacitor .6. 5-and\r.esi,ston.-6.1. simi ar mzthe second. parallel resonantcircuitfi Iv decoupled .tQ. the third .ffilter .69:,through: a pentode .1;l aiblockingwcapacitor :13

nandmesistor @115. ,ensriin standard practicerboth p n odes Bland "1 Iz:areprovidediwithan. automatic .cathodeebiasin i arrangement 15, 1.1;.re nective1y. Ad ion .emnlifi e iomand-.filterin a'ctiom are provideddn this case; a; d generative amplifier comprising. a dual-.triode. 19.:(t dime-6W). we pentode BI and the fourth parallel resonant circuit 83. This linear amplifying network (19, 8|, 33) is shown coupled to the third filter 59 through a blocking capacitor its output is taken from the last parallel resonant circuit or filter 83, as indicated by the arrows.

While in Fig. 1, the A.-C. voltages to be multiplied are shown as derived from separate oscillators (X and Y) whose outputs are controlled either manually or automatically by potentiometers P, it is obvious that the apparatus of the invention can be utilized to multiply two (or more) pairs (multiplier and multiplicand) of A.-C. voltages, however generated or derived. Similarly, and as previously indicated, any form of utilization device or circuit may be substituted for the meters (M) of Fig. 1.

The electrical values and. tube types marked on Fig. 2 were those employed in one practical embodiment of the invention, however, the inclusion of this information in this specification is not to be construed in a limiting sense since, obviously, the invention is susceptible of numerous other embodiments within the scope of the-appended claims.

What is claimed is:

1. Method of multiplying a multiplier and a. multiplicand, said method comprising generating two A.-C. voltages of different frequencies and of amplitudes proportional .respectively to said multiplier and multiplicand, generating a stream of electrons of a certain velocity, subjecting said electron stream to crossed electric and magnetic fields of an intensity and direction calculated to direct said stream in a straight path, subjecting said electron stream to an additional electric field of an intensity proportional to the resultant of said two A.-C. voltages whereby said electron stream tends to be deflected, causing the deflec :tion of said stream (resulting from the application of said A.-C. voltages of difierent frequencies to said crossed magnetic and electric fields) to generate an instantaneous potential, controlling the velocity of said electrons in accordance with said potential in the sense and to the degree re- .quired to substantially overcome the tendency of said electron stream to alter its path, and then deriving from said instantaneous potential a component which varies at a frequency which is equal 'to the sum or to the diiference of the frequencies of said multi lier and multiplicand voltages.

2. Method of operating an electron beam tube of the type operable in a magnetic field of constant intensity and containing an electron emissive cathode, an accelerating electrode, a pair of deflecting plates and a bi-part target, said method comprising applying a constant D.-C.

'voltagebetween said deflecting plates, superimposing a plurality of A.-C. voltages of difierent frequencies upon the D.-C. voltage applied between said deflecting plates to produce a deflection of said beam and a resulting difference in electron flow to the separate parts of said bi-part target, producing a signal voltage proportional to the instantaneous difference of the electron flow to said separate parts of said bi-part target, and

applying said signal voltage between said cathode equal to the sum or to the difierence of the frequencies of the A.-C. voltages applied to said deflecting plates.

4, Apparatus for obtaining an electrical value which is proportional to the product of two given A.-C. voltages of different frequencies, said apparatus comprising, in combination, an electron beam tube containing an electron-emisslve cathode, an accelerating electrode, a pair of deflecting electrodes and a bi-part target, means for generating and applying a magnetic field to said beam tube in a direction normal to the plane defined by the axis of said electron beam and the direction of the electric field between said deflecting plates, means for applying said A.-C. voltages to said deflecting plates whereby to produce a deflection of said beam and a resulting difierence in electron flow to the separate parts of said bipart target, means for producing a signal voltage proportional to the difference of the electron flow to said separate parts of said target, means for amplifying said signal voltage, means for applying said amplified signal voltage between the cathode and accelerating electrode of said beam tube in a manner tending to prevent deflection of said beam by said magnetic field and by the voltages applied between said deflecting plates,

and an electrical filter connected between said cathode and accelerating electrode and adapted to pass a frequency component of said signal voltage proportional to the sum or difierence of the frequencies of the voltages applied to said deflecting plates.

' JAN A.RAJCHMAN.

RICHARD L. SNYDER, JR. 

